This invention relates to check valves in micro-fluidic systems, and more particularly to an in-channel check valve.
Micropumps are devices that can pump and valve small volumes of fluids. A number of micropumps have been demonstrated, many of them diaphragm pumps utilizing check valves and piezoelectric actuation. Some of these micropumps have demonstrated low power consumption and reasonable flow rates, but out-of-plane fluid flow may be occur due to the absence of a good in-channel check valve for such micropumps.
Check valves are passive devices that may be opened for a forward fluid flow and closed for a reverse fluid flow. In micro-fluidic systems, check valves may be used individually in a channel to isolate fluid flow in a particular direction, or they may be used in pairs to direct fluid flows in micropumps.
It may be advantageous to provide an in-channel normally closed check valve that may be fabricated on a substrate with other micro-fluidic system components, e.g., micropumps and channels, to form an integrated micro-fluidic system.
A check valve assembly according to an embodiment may include an in-channel check valve connected between the front and rear portions of a channel. The check valve and the channel may both be attached to a common silicon substrate. The channel may have a width between about 10 xcexcm and about 400 xcexcm, and the check valve may have a width between about 50 xcexcm and about 500 xcexcm. The check valve may be generally circular in shape. The check valve may also be normally closed, that is, sealed in the absence of a pressure differential between the front and rear portions of the channel.
The check valve may include a sealing cap that contacts a valve seat to seal the valve. The sealing cap and the valve seat may each be formed from polymer membranes that are about 1 xcexcm to about 5 xcexcm thick. According to various embodiments, the polymer may be selected from Parylene, Mylar, polyurethane, and flourosilicone. The valve seat may include a metal layer of gold, or a chrome/gold multi-layer, to separate the contacting surfaces of the valve seat and the sealing cap in the closed position. The metal layer may be several hundred angstroms thick.
According to an embodiment, the check valve may open for forward fluid flows, that is, pressures that bias fluid flow from the front portion to the rear portion of the channel. The check valve may accommodate fluid flow rates in a range of about 1 nl/min to about 1 xcexcl/min.